1. Field of the Invention
The present invention relates to an optical pickup device for electronic devices such as personal computers and laptop computers.
2. Description of Related Art
Some of the conventional optical pickup devices incorporated in electronic devices such as personal computers and laptop computers use a laser light source that can emit laser light including two wavelengths to deal with different kinds of optical disks such as CDs and DVDs.
In some of such optical pickup devices, the emitted laser light is diffracted into a main beam (zero-order light) and a pair of side beams (±first-order light) so that a tracking control may be performed by receiving the light reflected from the optical disk During the process of reading and recording from and into the optical disk. Typically, a diffraction grating element is used for generating the side beams from the emitted laser light.
The optical disks sold on the market inevitably include some eccentricity, and it is necessary to correct the tracking error of the optical pickup device that is caused by the eccentricity so that the laser beam correctly follows the recording track of the optical disk. The influences of such an eccentricity on tracking control is greater toward the radially inner part of the optical disk, and a corresponding higher precision in the tracking control is required as the optical pickup head moves towards the radially inner part of the optical disk. The tracking control for different kinds of optical disks can be correctly accomplished by using a plurality of diffraction grating elements, but the use of a plurality of diffraction grating elements causes an increase in the size and cost of the optical pickup device.